Hydraulic roll-gap control system

ABSTRACT

A roll-gap control system comprising a doughnut-shaped cylinder, a correspondingly doughnut-shaped ram, a ram-position-detecting rod connected to the ram, and an electric scale having a movable part attached to the rod and a stationary part secured to a substantially unmovable fixed object.

United States Patent [191 Tanaka et al.

[451 Sept. 23, 1975 HYDRAULIC ROLL-GAP CONTROL SYSTEM Inventors: Shigeo Tanaka; Kazuyoshi Hashimoto, both of Hiroshima; Toshiharu Takatsu, lwakuni; Mitsuhiro Abe, Hiroshima; Hidetaki Sada, Hiroshima; Katsusuke Kawanami, Hiroshima, all of Japan 3,559,432 2/l97l Rastelli 72/2l X 3,736,782 6/1973 Fujino ct al 3,757,553 9/l973 Greenberger 72/238 X Primary E.\'aminerMilton S. Mehr Attorney, Ageht, 0r FirmToren, McGeady and Stanger [57] ABSTRACT A roll-gap control system comprising a doughnutshaped cylinder, a correspondingly doughnut-shaped ram, a ram-position-detecting rod connected to the ram, and an electric scale having a movable part attached to the rod and a stationary part secured to a substantially unmovable fixed object.

2 Claims, 3 Drawing Figures US Patent Sept. 23,1975

FIG.1

HYDRAULIC ROLL-GAP CONTROL SYSTEM This invention relates to a hydraulic roll-gap control system, particularly for rolling mills.

Heretofore, many different types of hydraulic adjusting equipments for roll-gap control have been proposed and manufactured. They include the arrangements in which the roll-gap control cylinder is installed in the upper or lower part of the roll-stand housing, and the roll-gap sensor is mounted in the control cylinder, in the back-up-roll or work-roll chock, or on top of the housing.

Of those known arrangements, the one having the roll-gap control cylinder installed in the lower part of the housing is widely in use. This is because any oil leakage from the cylinder cannot smear the strip being rolled, the pass line is easily kept constant despite the wear of the rolls, and the arrangement is easy to install.

As for the position where the roll-gap sensor is to be mounted, the top of the housing is preferred from the viewpoints of the atmosphere and maintenance. Since the top of the housing is subjected to most vigorous vibration, the arrangement usually employs a sensor incorporating a load cell or other such instrument of rugged construction.

The work-roll or back-up-roll chock, when chosen as a seat for the sensor, provides safety against vibration. However, whenever the rolls are to be replaced, the sensor must be detached, too. This adds to the labor and cost of roll replacement, apart from the difficulty involved in maintenance.

For the reasons stated, there has been no established technique of using a vibration-sensitive electric scale (e.g., inductosyn, S.E.A. type Te'lcote which is also known as magnetic scale, or differential transformer) as the roll-gap sensor and mounting the sensor in a hydraulic roll-gap control system.

The present invention has now been perfected with the foregoing in view. It is thus a principal object of the invention to provide a hydraulic roll-gap control system wherein an electric scale is used as a roll-gap sensor, and a rod is held through the lower part of a housing and the ceiling of an oil cellar, so that the electric scale detects the movement of the rod and therefore the amount of movement of a ram relative to a rollgap control cylinder.

Other objects, features, and advantages of the invention will become apparent from the following description, when taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a vertical sectional view of a conventional hydraulic roll-gap control system;

FIG. 2 is'a detail, in vertical section, of an embodiment of the invention; and

FIG. 3 is a detail, in vertical section, of another embodiment of the invention.

Referring to FIG. 1, there is shown a conventional hydraulic roll-gap control system wherein an electric scale is installed in an oil cellar by utilizing a rod mechanism for detecting the ram position in a roll-gap control cylinder. At a glance of the figure it would appear feasible without difficulty to install the electric scale in the oil cellar underneath the housing provided that the ordinary cylinder-ram-position detecting method is adopted. However, for the reasons to be given later, such an arrangement has been neither proposed nor realized.

in FIG. 1, a four-high roll stand equipped with an ordinary hydraulic roll-gap control system is shown as comprising a housing 1, upper and lower back-up rolls 2, 3, upper and lower work rolls 4, 5, a load cell 6 for roll-gap control, a roll-gap control cylinder 7, a ram 8, and a ram-position-detecting rod 9 with a head 9' engaging the ram 8. The rod 9 is connected, by means of a coupling 10, to an extension rod 11, which in turn is supported by a bearing 12 and associated at the lower end with an electric scale 13. The cylinder 7 is communicated with a computing element 14 via a servo valve 15. Also shown are an oil cellar 16 with a ceiling l6, and a watertight pipe 17.

The conventional system has the following disadvantages.

First, when the cylinder 7 is to be installed in or removed from the housing 1, it is moved together with the ram-position-detecting rod 9 secured in position. Care must, therefore, be used in handling them lest the rod should hit against other object.

Second, when the cylinder 7 demounted from the housing 1' is carried into the shop, it will have to be placed on a bench, about 2.5 meters high, to keep the rod 9 off the floor level.

Third, a packing fitted in the hole formed in the bottom center of the cylinder to receive the rod 9 therethrough cannot be maintained without removing the cylinder, in advance, from the housing 1.

Fourth, if the cylinder 7 is about 1,000 mm in diameter, a clearance of 0.6 to 0.8 mm will have to be provided between the cylinder and the ram 8 in order that the latter fits snugly in the former. The clearance will cause the upper portion of the ram 8 to slide horizontally, forcing the packing in the bottom center hole of the cylinder to serve as a fulcrum for the rod 9. Consequently the packing tends to break, often leading to an oil leak.

Fifth, as long as the oil pressure in the cylinder 7 is high, the force of friction between the packing in the bottom center hole of the cylinder is so weak, as compared with the force with which the oil pressure urges the rod 9 downward, that there is no problem at all. However, if the downward force is small and the pressure of the oil in the cylinder is low, the frictional force will no longer be negligible relative to the force that urges the rod 9 downward, and may result in an error in detection.

Sixth, because the rod 9 and the extension rod 11 are connected by means of the coupling, difficulty is involved in aligning those rods at the time of installation.

These are among many of the problems yet to be solved before the realization of a practical roll-gap control system.

The present invention is intended to remove all of the foregoing disadvantages. A roll-gap control cylinder and a gap-detecting rod assembly constructed in accordance with the invention has now made it possible to install an electric scale in an oil cellar without any of the shortcomings enumerated above.

The invention will be more fully described hereunder with reference specifically to FIG. 2 which shows a rollgap control cylinder and a detecting-end assembly of an embodiment the operation of which depends on the relative distance between a ram and the ground.

The hydraulic roll-gap control system according to the present invention is characterized in that the rollgap control cylinder is doughnut-shaped and associated with a ram which is also doughnut-shaped. so that a ramposition-detecting rod is connected at one end to the upper portion of the ram. without any chance of being immersed into the oil within the cylinder. and extended through a center hole of the doughnut cylinder down to an oil cellar, where the rod serves as a probe.

As shown. the roll-gap control cylinder 21 is formed with a center hole to what may be called a doughnut shape. The ram 22 too is doughnut-shaped with a center hole and fits snugly in the cylinder 21. While the cylinder in the embodiment being described does not provide a hydraulic pressure to force down or pull back" the ram. it is possible to modify the construction to pull the same back.

In the upper part of the rams center hole are fitted a cover 24 that keeps off coolant from the hole and a rod holder 25 that connects a ramposition-detecting rod 23 to the ram 22. The lower portion of the rod 23 is supported by a bearing 26, and the rod carries an electric scale 27 at its lower end. The scale 27 consists of a stationary part 28 and a movable part 29, the former being secured to the rod 23 and the latter to the foundation of an oil cellar.

FIG. 3 illustrates another embodiment of the invention. specifically the combination ofa modified roll-gap control cylinder and detecting end assembly the operation of which depends on the relative distance between the cylinder and the ram. This embodiment is preferred for installation with an oil cellar built on a soft ground.

In FIG. 3 there are shown a doughnut-shaped rollgap control cylinder 21 a doughnut-shaped ram 22. and a ram-position-detecting rod 23' connected at the upper end to the upper portion of the ram 22 and extending'downward through a fixed pipe 30. The upper end of the fixed pipe 30 is secured to the cylinder 21'. and the lower portion of the pipe is kept apart from the rod 23' by a bearing 26 in such a manner that the pipe and rod are slidable relative to each other. The lower end of the fixed pipe 30 that extends into an oil cellar carries a fixed part 28' of an electric scale 27'. while the lower end of the rod 23 holds a movable part 29' of the scale. The arrangement enables the electric scale 27' to determine the amount of relative movement of the two ends as the value representing the roll-gap of the rolling mill. For the purpose of the invention, the fixed pipe 30 may be replaced by a rod held in parallel with the ram-position-detecting rod 23'. It is further possible to secure the fixed pipe or rod unmovably to the housing 1 and attach the stationary part of the electric scale to the pipe or rod.

The merits and demerits of the two embodiments of the invention so far described in connection with FIGS. 2 and 3 will now be discussed.

First. the embodiment of FIG. 2 which measures the relative distance between the ram 22 and the ground. the mill constant is determined by the spring constant of the housing 1. rolls 2, 3. 4. or roll chock above the ram'22. whereas the mill constant of the second embodiment shown in FIG. 3 covers the spring constant of the entire mill.

Second. in the first embodiment the stationary part of the electric scale is not subjected to vibration direct from the rolling mill but, under certain circumstances, for example. where the ground is soft. its function may be affected by vibration from crane and/or other external source. In contrast to this. the stationary part 28 of the electrical scale in the second embodiment is not influenced by vibration from any external source. although it is slightly subjected to the vibration that mill produces as it receives and delivers the work through its rolls. An extra advantage of the latter embodiment is that. because the ram 30 and the rod 23 are substantially equal in length. mutual temperature compensation is attained.

Third. in the both embodiments. the larger the rollgap control cylinder 21 or 21'. the greater the clearance between the cylinder and the ram 22 or 22 will be. For example. with a cylinder about 1.000 mm in inside diameter the elearance will be as much as 0.6 to

0.8 mm. This large clearance can lead to a lateral movement of the ram 22 or 22' but. on the other hand. the ram-position-detecting rod 23 or 23' is so long (ab. 5 meters) that the movable and stationary parts of the electric scale 27 or 27 are held in parallel with ease and. moreover, the parallellism does not cause any disturbance of signals indicating the movements in the vertical direction.

Fourth. in the case not shown where the cylinder 21 or 21 is not so large in diameter and the clearance between the cylinder and the ram 22 or 22' is small. it will be possible to install the electric scale in the center hollow of the doughnut-shaped cylinder, that is. to close the bottom center of the cylinder and isolate the hollow from the outer atmosphere and then install an electric scale 27 or 27 therein to determine the relative positions of the cylinder and ram.

As compared with the conventional system shown in FIG. 1 which utilizes a ram-position-detecting rod mechanism. the system of the invention offers the following advantages.

First. because the cylinder and the ram in the present system are both doughnut-shaped. the ram-positiondetecting rod 23 or 23' and the cylinder 21 or 21 can be separately installed and then assembled together. although the system is similar to the prior art one in the fact that the rod is connected to the upper portion of the ram and that the electric scale is not mounted on the upper portion of the ram.

Second. the ram-position-detecting rod 23 or 23'. which is not immersed in oil as in the conventional system. has no possibility of contaminating the oil at the time of maintenance. This is beneficial for flashing. especially where a servo valve is employed. in which case the purity of oil is an important consideration.

Third. in fitting the doughnut-shaped ram into the doughnut-shaped cylinder. it is only necessary to provide a slightly more clearance between the inner periphery of the ram and the surrounding cylinder wall than between the outer periphery of the ram and the cylinder. This will enable the cylinder to receive the force of the ram along its outer periphery. and the small-diameter inner packing in the cylinder will not be subjected to the force that the conventional rod is given upon inclination of the ram.

Fourth. an improved detection accuracy is achieved by the omission of the coupling or other joint means usually required for the extension of the rod. The detecting end of the rod can be led into the oil cellar without difficulty.

In brief. according to the present invention, an electric scale is installed at a point of least vibration for the detection of the ram position in a roll-gap control cylinder, the cylinder and ram being both dough-nut shaped. and a ram-position-detecting rod is connected to the upper portion of the ram, the electric scale being mounted thereunder, so that the relative distance of movement between the ram on one hand and the cylinder, housing, or the ground on the other can be determined. Also, the detecting end of the rod can be easily extended down into the oil cellar. The invention thus provides a roll-gap control system of a great commercial value.

What is claimed is:

1. In a roll-gap control mechanism for a rolling mill including a plurality of rolls defining between a pair of said rolls a roll-gap through which a workpiece is fed,

said control mechanism including:

an hydraulic pistonand-cylinder assembly comprised of a stationary member fixed relative to said rolling mill and a movable member connected to move in accordance with relative movement of said rolls to vary the size of said roll-gap,

a position rod fixed to said movable member and sensing means for generating a control signal indicative of variations in said roll-gap in response of movement of said position rod,

the improvement wherein:

said stationary member is configured as a generally upwardlyopening cupped member including an upstanding outer annular wall,

an upstanding inner annular wall located radially inwardly of and generally concentrically with said outer annular wall,

a centrally located open-ended hole extending through said stationary member defined and surrounded by said inner annular wall, and

an annular trough defined between said inner and outer annular walls;

said movable member is configured as a generally downwardly opening cupped member including a depending annular wall extending within said annular trough in sealed sliding engagement between said upstanding inner and outer annular walls; and

said position rod extends from fixed engagement with said movable member to said sensing means through said centrally located hole.

2. A mechanism according to claim 1, wherein said sensing means comprise a movable part fixed to said position rod and a stationary part fixed to said stationary member of said piston-and-cylinder assembly, with relative movement between said movable and stationary parts of said sensing means providing an indication of variation in said roll-gap. 

1. In a roll-gap control mechanism for a rolling mill including a plurality of rolls defining between a pair of said rolls a roll-gap through which a workpiece is fed, said control mechanism including: an hydraulic piston-and-cylinder assembly comprised of a stationary member fixed relative to said rolling mill and a movable member connected to move in accordance with relative movement of said rolls to vary the size of said roll-gap, a position rod fixed to said movable member and sensing means for generating a control signal indicative of variations in said roll-gap in response of movement of said position rod, the improvement wherein: said stationary member is configured as a generally upwardlyopening cupped member including an upstanding outeR annular wall, an upstanding inner annular wall located radially inwardly of and generally concentrically with said outer annular wall, a centrally located open-ended hole extending through said stationary member defined and surrounded by said inner annular wall, and an annular trough defined between said inner and outer annular walls; said movable member is configured as a generally downwardly opening cupped member including a depending annular wall extending within said annular trough in sealed sliding engagement between said upstanding inner and outer annular walls; and said position rod extends from fixed engagement with said movable member to said sensing means through said centrally located hole.
 2. A mechanism according to claim 1, wherein said sensing means comprise a movable part fixed to said position rod and a stationary part fixed to said stationary member of said piston-and-cylinder assembly, with relative movement between said movable and stationary parts of said sensing means providing an indication of variation in said roll-gap. 